NASA feels it has a good shot at sending shuttle Discovery to the international space station on Sunday.

While the agency still doesn’t know what caused a hydrogen gas leak that prevented the space shuttle from flying earler this week, officials say they are hopeful repairs have solved the problem.

Leaking hydrogen gas — a dangerous situation because it could ignite and cause an explosion — forced NASA to call off Wednesday’s launch attempt.

The space shuttle is scheduled to blast off Sunday evening.

Discovery is more than a month late for its scheduled trip to the international space station.

First, hydrogen gas valves inside the shuttle had to be double-and-triple-checked. Then on Wednesday, hydrogen gas began leaking during fueling where a vent line hooks up to the external fuel tank.

(Source: Fox News)